It's pretty clearly designed to allow you to destroy your own indestructible lands, and doesn't include the caveat "opponent"
The strength and synergy of the Elf typal strategy make it so easy for newer players to be somewhat competitive in a given pod
Since you get two lore when the false king quests, youre making a four-point lore shift in the game, which is pretty significant especially if youre able to quest multiple times in a game
But you can get value out of her even earlier than that, with the four cost item Eye of the Fates from Disney Lorcanas first set
Interestingly enough, there are 11 cards that don't have the Assassin card type, but reference the Assassin type in the text, such as Origin of the Hidden Ones, Vraska the Unseen, and Brotherhood Headquarters (which feels like it should get an honorable mention)
"A Japanese RPG Primer: The Essential 20"